How to care for secondary batteries: NiCd - keep them cool, cycle them shallowly, occasionally deep discharge them and recharge them. NiMH - keep them cool, cycle them shallowly. No need for deep cycles (it just wears them out faster.) Lead-acid - keep them cool, keep them fully charged as much as possible, cycle them shallowly. Do not allow them to discharge completely during storage. Lithium ion - keep them cool, keep them at 30-50% charge as much as possible. Shallow cycles. Do not store fully charged and do not store completely discharged.